From European patent application EP 1 411 008 A1 a so-called tilt-tray sorting device is known, in which an endless train of sorting units is used. Each sorting unit has a chassis and a carrier deck, which is capable of lateral tilting movement relative to the chassis. Each sorting unit is provided with an electric motor for tilting the carrier deck. Tilting the carrier deck makes it possible to cause a product supported by the load-bearing deck to slide off the load-bearing deck at a sorting location. A risk that plays a role in this regard is that a piece of luggage will catch on something or stick to the load-bearing deck while being handled, for example because a strap catches on a corner of the carrier deck or because a piece of luggage is wet or wrapped in shrink foil, as a result of which the piece of luggage will remain present on the carrier deck or slides off the tilting deck at least in an uncontrolled direction rather than in lateral direction in spite of the tilting of the carrier deck, as a result of which the correct functioning of an upstream sorting unit, of a downstream sorting unit or of the sorting unit in question itself, and thus of the entire sorting device will be at risk. Another drawback of the known sorting device is the fact that it is relatively costly, in particular for applications where a limited number of pieces of luggage are to be handled, for example 3000 pieces of luggage per hour, which is a usual capacity at medium-sized airports.
A sorting device as referred to in the introduction is known from U.S. Pat. No. 4,732,260. Said document discloses a sorting device comprising a plurality of elongated plates positioned one behind the other, which are oriented transversely to a conveying direction, which plates follow an endless conveying path in the vertical plane. The upper sides of the upper halves of the plates each form a supporting surface for a product to be sorted. A pusher element is provided for each plate, which pusher element is capable of reciprocating motion transversely to the conveying direction between two opposite ends of the respective plate for thus pushing a product off the plate at a sorting location. The pusher element is to that end connected, via a slot in the associated plate, to a block-shaped driving element present on the opposite side of the plate. Said driving element is provided with two bores, through which two guides extending transversely to the conveying direction and being rigidly connected to the plate in question are movable. A guide element provided with three rollers arranged one behind the other, which rollers are to cooperate with the aforesaid stationary guide, is mounted under the driving element via a vertical pivot pin. An important drawback of this known sorting device is that it is not suitable for sorting pieces of luggage. From a practical viewpoint this is caused by the fact that the slot that is present in each plate for the necessary connection between the pusher element on the outer side of the plate and the driving element on the inner side of the plate constitutes the risk that projecting parts, such as straps and handles of pieces of luggage will get stuck therein. From an economic viewpoint there is furthermore the fact that the device is too expensive for being used in an economically sound manner with pieces of luggage, in which connection it should be realised that in view of the dimensions of each plate, seen in the conveying direction, a relatively large number of plates provided with the associated parts as described above are needed. In addition to that, the pusher elements associated with a number of successive plates move from one side of the sorting device to the opposite side transversely to the conveying direction upon sorting out a piece of luggage, to which end the guide elements associated with the pusher elements in question move along the same stationary guides. During this movement, the pusher elements jointly form a pushing plane oriented at an angle to the conveying direction, causing the orientation of the pieces of luggage on the associated plates to change. This is not always desirable. Another important drawback is the risk that the pusher element tends to take up an oblique position as soon as a force is exerted thereon at an off-centre location along the length of the pusher element. This will adversely affect the guiding cooperation between the transverse guides and the two bores in the driving element and result in increased mechanical resistance and thus extra wear on various related parts. This adverse effect becomes stronger as the length of the pusher element increases.